With evolution of a mobile communications network and continuous emergence of a large quantity of new applications, different users gradually form different communication features in different application fields, and therefore different communication types are generated, for example, machine type communication (Machine Type Communication, MTC for short), mobile virtual network communication, and public safety communication. Currently, operators put forward a requirement for deploying different dedicated core networks (Dedicated Core Network, DCN) for different communication types. The operators subscribe to one type of dedicated core network (DCN) for terminals that support a same communication type, and deploy a special core network element for the terminals, so that the terminals that support the same DCN register with the core network element specially deployed for the terminals. This helps the operators perform specific management and maintenance on terminals that support different DCNs, so as to improve efficiency in accessing a network by a terminal, and reduce network maintenance costs.
Based on a current plan of the 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP for short), a plurality of different types of DCNs may be simultaneously configured for one core network element in a public land mobile network (Public Land Mobile Network, PLMN for short). In addition, to avoid extremely heavy load on the core network element, a backoff policy is used when congestion occurs in the network. Specifically, when congestion occurs in the network, a network side may determine to perform congestion control on a DCN in a plurality of currently supported DCNs. In this case, if a terminal that supports the DCN on which congestion control is performed initiates a radio connection request for accessing the network, the terminal is rejected by a radio access network node (Radio Access Network Node, RAN Node), and thereby is unable to access the network, so that network load is alleviated. In addition, the RAN node specifies a time for which the terminal needs to back off. After waiting for the backoff time specified by the RAN node, the terminal re-initiates a radio connection request, to attempt to re-access the network.
In the foregoing solution, when network congestion is serious, after backing off and waiting a plurality of times, the terminal may be still unable to access the network. Consequently, a service of the terminal cannot be carried out, and user service experience is accordingly degraded.